The Multiphase Intergalactic Medium toward PKS 2155-304
Abstract
We study the cluster of H I and O VI absorption systems and the claimed detection of O VIII absorption from the intergalactic medium at z~0.0567, associated with a group of galaxies toward the BL Lac object PKS 2155-304. As measured by spectrographs on the Hubble Space Telescope, Far Ultraviolet Spectroscopic Explorer, and Chandra, this system appears to contain gas at a variety of temperatures. We analyze this multiphase gas in a clumpy-infall model. From the absence of C IV and Si III absorption in the Lyα clouds, we infer metallicities less than 2.5%-10% of solar values. The only metals are detected in two O VI absorption components, offset by +/-400 km s-1 from the group barycenter (cz~16,600 km s-1). The O VI components may signify ``nearside'' and ``backside'' infall into the group potential well, which coincides with the claimed O VIII absorption. If the claimed O VIII detection is real, our analysis suggests that clusters of strong Lyα and O VI absorbers, associated with groups of galaxies, may be the ``signposts'' of shock-heated metal-enriched baryons. Through combined UV and X-ray spectra of H I and O VI, O VII, and O VIII, one may be able to clarify the heating mechanism of this multiphase gas.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2003
- DOI:
- 10.1086/378737
- arXiv:
- arXiv:astro-ph/0307004
- Bibcode:
- 2003ApJ...594L.107S
- Keywords:
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- Galaxies: Intergalactic Medium;
- Astrophysics
- E-Print:
- Accepted for ApJL (2003), 11 pages, 1 color figure